Dairy products are a staple in the American household thanks its high nutritional value in vitamin D, magnesium, calcium and potassium. Because it’s widely consumed, dairy farms constantly deliver raw milk to dairy processors all 365 days of the year. Garelick Farms, one of New England’s largest dairy suppliers, is one of the places that processes fluid milk for sale in grocery stores across the region.
Some of these dairy processes produce wastewater, which requires Garelick Farms to treat the water onsite. The treatment process involves two steps:
At the bottom of the fermenter tank, a membrane separates milk fats, milk solids and organic solids from the liquid so its solids can be digested by anaerobic bacteria.
Inside the bottom of a re-aeration tank, very small air bubbles are injected into the water by aerators. These fine bubbles transfer oxygen to the water, assisting aerobic bacteria in producing enzymes that further break down waste.
For several years, Garelick Farms used positive displacement blowers to supply air for re-aeration. However, the farm quickly realized that they needed a higher volume of compressed air for the increasing membrane capacity so they invested in a rotary screw blower, an Atlas Copco ZS VSD. The new blower realized a savings of $22,000 a year, which shortened the payback period to just over a year.
At Garelick Farms, the screw blower’s speed varies according the wastewater’s dissolved oxygen (DO) level, which changes based on pure volume and effluent composition. The aeration tank’s sensor reads the DO level and converts the value to blower speed. If the DO drops below the low end of the operating range, more oxygen is required. Therefore, the blower will increase its speed until the DO level returns to normal. On the other hand, if the DO level is too high, less oxygen is required and the sensor sends a signal to slow down the blower.
In addition to increased energy efficiency, the ZS VSD has also reduced noise in the utility room to 72 dB(A) where hearing protection is no longer required. The screw blower has been a big upgrade for Garelick Farms and has the potential to help your wastewater needs as well. Interested in learning more? Contact an Atlas Copco expert today for more information.